Hess Triangle
"Property of the Hess Estate which has never been dedicated for public purposes."
This is a triangle at the intersection of Seventh Ave and Christopher Street in New York's West Village. From Wikipedia: "The plaque is the result of a dispute between the city government and the estate of David Hess, a landlord from Philadelphia who owned the Voorhis, a five-story apartment building. In the 1910s the city claimed eminent domain to expropriate and demolish hundreds of buildings in the area in order to widen Seventh Avenue and expand the IRT subway. According to Ross Duff Wyttock, writing in the Hartford Courant in 1928, Hess's heirs discovered that, when the city seized the Voorhis, the survey had missed this small corner of the plot and they set up a notice of possession. The city asked the family to donate the diminutive property to the public, but they refused and installed the present, defiant mosaic on July 27, 1922. In 1938 the property, reported to be the smallest plot in New York City, was sold to the adjacent Village Cigars store for $1,000 (approximately $17,000 adjusted for inflation in 2016), approximately $2 per square inch. The new owners left the plaque in place and, as of 2015, it remains."
https://en.wikipedia.org/wiki/Hess_triangle